The Transformer version of the 40M EH antenna.

This version is much easier to make and also easier to set up. The performance is slightly lower than the full network antenna being wider bandwidth but at 40m I did not think this much of a loss. I found it more height tolerable as well relative to frequency changes and impedance matching. The core of the antenna again was made out of pvc sheet 4 inches wide that just fitted inside the toilet pipe. The cylinders again were made out of brass but longer at seven inches in length with a diameter of 3 and 3 quarter inches. In the four inch space between the cylinders I fitted a paper tube made up out of glued together rolled up cartdrige paper , the tube being the same dia as the brass tubes. The wall thickness being just under 1/8 in thick. This was then thoroughly laquered. This tube is the base on which to wind the transformer coil secondary which the ends of which are connected to the two cylinders as in the 14mhz and 18 mhz version in my other article.

The difference here is that the two turn primary which is connected across the co-ax feeder is at the bottom of the coil not in the center. The co-ax braid is connected by a short link to the top of the bottom cylinder. The co-ax is then fed out via the center of the tubes tied in place with tie wraps. The whole construction is a tight fit in the soil pipe which is the weather jacket. The secondary coil was made out of 16swg laquered copper wire. The two turn primary out of thin multistrand connecting wire wound 3/16 of an inch below the secondary winding. The windings were held in place with pvc tape. In the picture below you can see the hole where the coax connects to the two turn primary loop and the link to the bottom cylinder. The secondary winding connection to the bottom cylinder is inside the tube. The secondary winding connection to the top cylinder is the one visible at the right. The cylinders are thin sheet brass but could be copper sheet , tinplate or aluminium.

Tuning it up.

Very simply you can not beat an MFJ antenna bridge. In my case I used a short six feet cable to connect to the antenna while it was still sitting on the kitchen table. I then swept the antenna looking at the bridge for X=0 and the match as the tuned frequency was found. I had started with 20 turns of wire and this was far too much as I had a good antenna at 5 mhz or so. I now altered the co-ax cable length and got the same measurements. I then put the antenna up on the mast and got very similar measurements again but the vswr had gone up. The next step was to strip it apart again , remove turns on the top of the primary and measure again each time until 7 mhz was reached. The vswr match was down to 1.2 to 1 at this stage so it just turned out nicely. After connecting the rig to the aerial I found that the rig agreed with the results measured so far by sending 100 watts into the antenna at frequencies between 7mz and 7.1 mhz. I then set the rig in the middle of the band and set a carrier to 10 watts. Using the field strength meter I was glad to find a strong field in the vicinity of the antenna. At this time you are always bursting to have a QSO and guess what, at this time there had been a flare and 40m was as flat as the proverbial pancake. However at later dates reports showed that I had a usable antenna.